1. Field
The subject matter disclosed herein relates to using local maps and annotations for location determination.
2. Information
Different techniques may be used to estimate the location of a mobile device, such as a cell phone, personal digital assistant (PDA), or any other mobile device. For example, some mobile devices may process signals received from a Satellite Positioning System (SPS) to estimate their locations. However, sometimes there are certain areas where navigation signals from an SPS may not be available, such as in certain indoor locations.
A mobile device may estimate its location within an area where navigation signals transmitted from an SPS are not available. For example, a mobile device may transmit a signal to an access point and measure a length of time until a response signal from the access point is received. A range from the mobile device to the access point may be determined based upon the measured length of time between transmission of a signal from the mobile device and receipt of a response signal at the mobile device. Alternatively, signal strength of a signal received from the access point may be measured and a range from the mobile device to the access point may be estimated based on the measured signal strength. An access point may comprise a device that allows wireless communication devices to communicate with a network.
However, an access point may experience a processing delay between a time at which a signal is received from a mobile device and a time at which a response signal is transmitted to the mobile device. Such a processing delay may vary depending upon a particular access point, and may need to be accounted for when a mobile device estimates a range to the access point based on the measured time interval. Moreover, signal strength of a received signal may vary based upon physical structures within an area, such as a presence of ceiling and walls, causing a variance in received signal strength which may result in inaccurate estimates of range to the access point if there is no accounting for such a variance caused by a presence of physical structures, for example.